Activation of STING requires palmitoylation at the Golgi

Discovery of indole derivatives as STING degraders

Aberrant activation of the stimulator of interferon genes (STING) pathway is associated with the development of various inflammatory and autoimmune diseases. Targeting STING for degradation represents a novel strategy for the treatment of these diseases. In this study, we designed and synthesized a series of STING-PROTACs based on a nitro-free covalent warhead and different E3 ligase binders. The representative compound 2h specifically degraded STING protein through the proteasome pathway with a DC50 value of 3.23 μM and exhibited sustained degradation activity over 72 h. Further biological studies demonstrated that compound 2h inhibited STING signaling and effectively suppressed immune-inflammatory cytokines both in vitro and in vivo. Moreover, compound 2h offered better safety compared to its warhead molecule and SP23. Collectively, compound 2h is a potent nitro-free covalent STING degrader and warrants further investigation.

MINT3 promotes STING activation and facilitates antiviral immune responses

Stimulator-of-interferon genes (STING) translocation is the rate-limiting step in the cGAS-STING signaling which detects cytosolic DNA and produces type I interferons. However, the mechanism by which this process is modulated remains to be further clarified. In the present study, we identified munc18-1-interacting protein 3 (MINT3) as a positive regulator of STING signaling. MINT3 promotes type I interferons production induced by herpes simplex virus-1 (HSV-1) infection and ISD or cGAMP stimulation in mouse peritoneal macrophages. Deficiency of Mint3 greatly inhibited STING and IRF3 activation in macrophages. Mint3 knockdown also attenuated STING and IRF3 activation in macrophages, human THP-1 cells, and RAW264.7 cells. Mechanistically, MINT3 interacted with STING, selectively enhanced its K63-linked polyubiquitination and facilitated STING translocation to the Golgi, resulting in the enhancement of the STING and TBK1 interaction. Furthermore, MINT3 also facilitated HSV-1-induced innate antiviral immune responses and impaired HSV-1 replication in vitro and in vivo. Interestingly, we showed that the expression of MINT3 was dramatically elevated during HSV-1 infection, and ISD stimulation in macrophages. Thus, we have revealed a feedback mechanism for the regulation of the cGAS-STING pathway, providing a promising therapeutic target for the treatment of disorders triggered by aberrant STING activity.

STING inhibitors and degraders: Potential therapeutic agents in inflammatory diseases

The regulation of the STING (stimulator of interferon genes) pathway represents a promising target for a range of inflammatory diseases. This review provides an overview of the structure of STING and discusses the mechanisms by which the cyclic GMP-AMP synthase (cGAS)-STING pathway is associated with various autoinflammatory and autoimmune diseases. We explore how targeting STING inhibition or degradation can alleviate excessive inflammatory signaling and improve efficacy. Emerging strategies include inhibiting STING expression by covalently binding compounds or using ligands that target the binding pocket. In addition, selective degradation of STING via the ubiquitin-proteasome system or the lysosomal pathway shows promise. In addition, we explore the implications of modulating the cGAS-STING pathway in the context of various inflammatory diseases. Finally, we summarize the chemical properties of recently developed STING compounds and their potential clinical applications. By comprehensively reviewing the current understanding of the role of STING in inflammation and the therapeutic potential of targeting STING, we aim to identify new avenues of intervention that could improve outcomes for patients with inflammatory diseases. This review highlights the important role of STING in the regulation of inflammation and its potential as a target for innovative therapeutic strategies.

Unveiling EXOC4/SEC8: a key player in enhancing antiviral immunity by inhibiting the FBXL19-STING1-SQSTM1 signaling axis

As a core aptamer for anti-DNA viral immunity, STING1 (stimulator of interferon response cGAMP interactor 1) is tightly regulated to ensure the proper functioning of the natural antiviral immune response. However, many mechanisms underlying the regulation of STING1 remain largely unknown. In this study, we identify EXOC4/SEC8 (exocyst complex component 4) as a novel positive regulator of DNA virus-triggered type I interferon signaling responses through stabilizing STING1, thereby inhibiting DNA viral replication. Mechanistically, EXOC4 suppresses K27-linked ubiquitination of STING1 at K338, K347, and K370 catalyzed by the E3 ligase FBXL19 (F-box and leucine rich repeat protein 19), thereby preventing ubiquitinated-STING1 from recognition by SQSTM1 (sequestosome 1) for autophagic degradation. Importantly, mice conditionally knocked out for Exoc4/Sec8 are more susceptible to herpes simplex virus type 1 (HSV-1) infection and exhibit more severe lung pathology compared to control mice. This further confirms the important role of EXOC4/SEC8 in antiviral natural immunity. Taken together, our study reveals the importance of EXOC4/SEC8 in promoting STING1-centered antiviral natural immunity and highlights its potential as an anti-DNA viral therapeutic target.

Unraveling the cGAS-STING pathway in Alzheimer's disease: A new Frontier in neuroinflammation and therapeutic strategies

Alzheimer's disease (AD) is the most prevalent type of neurological disorder characterized by cognitive decline and memory loss, marked by the accumulation of amyloid beta (Aβ) plaques and hyperphosphorylated tau protein, causing extensive neuronal death and neuroinflammation. There is growing evidence that AD development extends beyond the neuronal compartment and has a major impact on the immunological functions of the brain. The cyclic GMP-AMP synthase (cGAS) detects cytosolic DNA, including pathogenic foreign DNA and self-DNA from cellular injury, triggering a type I interferon (IFN-I) response through activation of the stimulator of interferon genes (STING). The activation of the cGAS-STING pathway in response to mitochondrial dysfunction drives neuroinflammation in AD, which is mediated by the release of IFN-I cytokines. Furthermore, the release of oxidized mtDNA is necessary for the stimulation of the nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome, which is a family of protein complexes that macrophages can produce to induce inflammation. AD becomes severe by the stimulation of the cGAS-STING pathway, which results in sterile inflammation and microglial dysfunction. This review aims to explore the potential impact of the cGAS-STING signaling pathway in the pathogenesis and progression of AD. Additionally; after overviewing recent findings, this article highlights the molecular mechanism involved in the onset of disease and its modulation regarding the therapeutic approach of AD. Finally, deliberated a deep insight, the cGAS-STING axis could provide novel therapeutic avenues for slowing or halting the progression of AD, thereby offering new prospects for treatment development.

Protein lipidation in the tumor microenvironment: enzymology, signaling pathways, and therapeutics

Protein lipidation is a pivotal post-translational modification that increases protein hydrophobicity and influences their function, localization, and interaction network. Emerging evidence has shown significant roles of lipidation in the tumor microenvironment (TME). However, a comprehensive review of this topic is lacking. In this review, we present an integrated and in-depth literature review of protein lipidation in the context of the TME. Specifically, we focus on three major lipidation modifications: S-prenylation, S-palmitoylation, and N-myristoylation. We emphasize how these modifications affect oncogenic signaling pathways and the complex interplay between tumor cells and the surrounding stromal and immune cells. Furthermore, we explore the therapeutic potential of targeting lipidation mechanisms in cancer treatment and discuss prospects for developing novel anticancer strategies that disrupt lipidation-dependent signaling pathways. By bridging protein lipidation with the dynamics of the TME, our review provides novel insights into the complex relationship between them that drives tumor initiation and progression.

Palmitoyl-transferase 3 promotes mitochondrial antiviral signaling protein degradation by modulating its ubiquitination

The innate antiviral immunity of humans serves as their first line of defence against viral and microbial illnesses. The retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) signaling pathway requires the mitochondrial antiviral signaling protein (MAVS) to function properly. ZDHHCs, a family of acyltransferases, regulate diverse biological processes via interactions with numerous mammalian proteins and viral proteins. However, the role of ZDHHCs in antiviral innate immunity against RNA viruses remains largely elusive. Here, we show that ZDHHC3 downregulates the RLR signaling pathway. Ectopic ZDHHC3 expression reduces RIG-IN- and SeV-mediated IFN-β promoter activity, IRF3 nuclear transduction, and transcription of the IFN-β and ISG genes. Furthermore, ectopic expression of ZDHHC3 decreases MAVS stability by promoting proteasomal degradation, which can be reversed by MG132 but not CQ. ZDHHC3 interacts with MAVS and promotes its breakdown by increasing K48-linked ubiquitination rather than K63-linked ubiquitination. ZDHHC3 deletion resulted in increased IFN-β promoter activity and transcription of the IFN-β and ISG genes. ZDHHC3 knockdown promotes subsequent antiviral signaling and reduces viral replication, indicating the role of ZDHHC3 in antiviral innate immunity. In addition, the catalytically inactive mutant ZDHHC3 C157S efficiently reversed the IFN-β promoter activity produced by RIG-IN, which was consistent with the results of 2-BP treatment. Collectively, these data show that ZDHHC3 inhibits the RNA virus-triggered signaling cascade by targeting MAVS and provides new insights into the role of ZDHHC3 in antiviral innate immunity.

cGAS-STING: mechanisms and therapeutic opportunities

The cGAS-STING pathway plays a crucial role in the innate immune system by detecting mislocalized double-stranded DNA (dsDNA) in the cytoplasm and triggering downstream signal transduction. Understanding the mechanisms by which cGAS and STING operate is vital for gaining insights into the biology of this pathway. This review provides a detailed examination of the structural features of cGAS and STING proteins, with a particular emphasis on their activation and inhibition mechanisms. We also discuss the novel discovery of STING functioning as an ion channel. Furthermore, we offer an overview of key agonists and antagonists of cGAS and STING, shedding light on their mechanisms of action. Deciphering the molecular intricacies of the cGAS-STING pathway holds significant promise for the development of targeted therapies aimed at maintaining immune homeostasis within both innate and adaptive immunity.

Distinct pathogenic mutations in ARF1 allow dissection of its dual role in cGAS-STING signalling

Tight control of cGAS-STING-mediated DNA sensing is crucial to avoid auto-inflammation. The GTPase ADP-ribosylation factor 1 (ARF1) is crucial to maintain cGAS-STING homeostasis and various pathogenic ARF1 variants are associated with type I interferonopathies. Functional ARF1 inhibits STING activity by maintaining mitochondrial integrity and facilitating COPI-mediated retrograde STING trafficking and deactivation. Yet the factors governing the two distinct functions of ARF1 remained unexplored. Here, we dissect ARF1's dual role by a comparative analysis of disease-associated ARF1 variants and their impact on STING signalling. We identify a de novo heterozygous s.55 C > T/p.R19C ARF1 variant in a patient with type I interferonopathy symptoms. The GTPase-deficient variant ARF1 R19C selectively disrupts COPI binding and retrograde transport of STING, thereby prolonging innate immune activation without affecting mitochondrial integrity. Treatment of patient fibroblasts in vitro with the STING signalling inhibitors H-151 and amlexanox reduces chronic interferon signalling. Summarizing, our data reveal the molecular basis of a ARF1-associated type I interferonopathy allowing dissection of the two roles of ARF1, and suggest that pharmacological targeting of STING may alleviate ARF1-associated auto-inflammation.

Oxaliplatin accelerates immunogenic cell death by activating the cGAS/STING/TBK1/IRF5 pathway in gastric cancer

Immunogenic cell death is a tumor cell death involving both innate and adaptive immune responses. Given the published findings that oxaliplatin causes the secretion of high mobility group box 1 (HMGB1) from cancer cells, which is necessary for the initiation of immunogenic cell death, we investigated whether oxaliplatin plays an anticancer role in gastric cancer by inducing immunogenic cell death and further explored its mechanism. We found that oxaliplatin inhibited viability and induced pyroptosis, immunogenic cell death, the production of reactive oxygen species, mitochondrial permeability transition pore (mPTP) opening, and cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) axis activation in gastric cancer cells. Suppressing mPTP opening (cyclosporine treatment), depleting mitochondrial DNA (mtDNA; ethidium bromide treatment), or STING downregulation (H151 or si-STING treatment) reversed cGAS/STING pathway activation and the increased immunogenic cell death induced by oxaliplatin in MKN-45 and AGS cells. Moreover, oxaliplatin induced immunogenic cell death via activating the cGAS/STING/TANK-binding kinase 1 (TBK1; also known as serine/threonine-protein kinase TBK1)/interferon regulatory factor 5 (IRF5) pathway. In conclusion, oxaliplatin treatment could induce immunogenic cell death and mPTP opening and activate the cGAS/STING/TBK1/IRF5 pathway in gastric cancer cells.

[Research Progress and Applications of ZDHHC-mediated Protein Palmitoylation in the Development and Immune Escape of Non-small Cell Lung Cancer]

Non-small cell lung cancer (NSCLC), a leading cause of cancer-related deaths worldwide, remains a significant clinical challenge despite advances in immune checkpoint inhibitors therapy, with drug resistance persisting as a major obstacle. Palmitoylation, a critical post-translational modification (PTM) primarily catalyzed by palmitoyltransferases of the zinc finger DHHC-type (ZDHHC), has recently demonstrated important implications in NSCLC. This review aims to elucidate the mechanisms and clinical potential of ZDHHC-mediated protein palmitoylation in NSCLC progression and immune escape.
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Oligomerization of STING and Chemical Regulatory Strategies

Stimulator of interferon genes (STING) plays a crucial role in innate immunity. Upon the recognition of cytosolic dsDNA, STING undergoes several structural changes, with oligomerization playing a key role in initiating a cascade of immune responses. Therefore, controlling the STING pathway by manipulating STING oligomerization is a practical strategy. This review focuses on the detailed mechanism of STING oligomerization, highlighting its decisive role. It also describes oligomerization-based strategies to regulate STING protein, such as the use of small-molecule agonists and biomacromolecules, highlighting their interaction modes and potential therapeutic applications. This knowledge may lead to the development of innovative approaches for treating cancer and immune disorders.

cGAS-STING signaling in melanoma: regulation and therapeutic targeting

Melanocytes are the source of the skin cancer known as melanoma. It usually affects the viscera, mucous membranes, and skin. Even so, melanoma only makes for 7% of all skin cancer occurrences. By triggering the generation of type I interferons (IFN-I) and inflammatory cytokines upon identifying microbial DNA, the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway promotes anti-microbial innate immunity. A growing body of research indicates that antitumor immunity depends on the cGAS-STING axis being activated. The cGAS-STING-regulated downstream cytokines, particularly IFN-I, act as linkages between adaptive and innate immunity. As a result, an increasing amount of research has concentrated on the synthesis and screening of agonists of the STING pathway. As a result, an increasing amount of research has concentrated on the synthesis and screening of agonists of the STING pathway. The many implications of the cGAS-STING pathway in the pathophysiology and therapy of melanoma are thoroughly examined in this study. Our research highlights the significance of the cGAS-STING pathway in melanoma and identifies it as a key target for boosting immunity against tumors.

Unveiling the crossroads of STING signaling pathway and metabolic reprogramming: the multifaceted role of the STING in the TME and new prospects in cancer therapies

The cGAS-STING signaling pathway serves as a critical link between DNA sensing and innate immunity, and has tremendous potential to improve anti-tumor immunity by generating type I interferons. However, STING agonists have shown decreasing biotherapeutic efficacy in clinical trials. Tumor metabolism, characterized by aberrant nutrient utilization and energy production, is a fundamental hallmark of tumorigenesis. And modulating metabolic pathways in tumor cells has been discovered as a therapeutic strategy for tumors. As research concerning STING progressed, emerging evidence highlights its role in metabolic reprogramming, independent its immune function, indicating metabolic targets as a strategy for STING activation in cancers. In this review, we delve into the interplay between STING and multiple metabolic pathways. We also synthesize current knowledge on the antitumor functions of STING, and the metabolic targets within the tumor microenvironment (TME) that could be exploited for STING activation. This review highlights the necessity for future research to dissect the complex metabolic interactions with STING in various cancer types, emphasizing the potential for personalized therapeutic strategies based on metabolic profiling.

A non-canonical cGAS-STING pathway drives cellular and organismal aging

Accumulation of cytosolic DNA has emerged as a hallmark of aging, inducing sterile inflammation. STING (Stimulator of Interferon Genes) protein translates the sensing of cytosolic DNA by cGAS (cyclic-GMP-AMP synthase) into an inflammatory response. However, the molecular mechanisms whereby cytosolic DNA-induced cGAS-STING pathway leads to aging remain poorly understood. We show that STING does not follow the canonical pathway of activation in human fibroblasts passaged (aging) in culture, senescent fibroblasts, or progeria fibroblasts (from Hutchinson Gilford Progeria Syndrome patients). Despite cytosolic DNA buildup, features of the canonical cGAS-STING pathway like increased cGAMP production, STING phosphorylation, and STING trafficking to perinuclear compartment are not observed in progeria/senescent/aging fibroblasts. Instead, STING localizes at endoplasmic reticulum, nuclear envelope, and chromatin. Despite the non-conventional STING behavior, aging/senescent/progeria cells activate inflammatory programs such as the senescence-associated secretory phenotype (SASP) and the interferon (IFN) response, in a cGAS and STING-dependent manner, revealing a non-canonical pathway in aging. Importantly, progeria/aging/senescent cells are hindered in their ability to activate the canonical cGAS-STING pathway with synthetic DNA, compared to young cells. This deficiency is rescued by activating vitamin D receptor signaling, unveiling new mechanisms regulating the cGAS-STING pathway in aging. Significantly, in HGPS, inhibition of the non-canonical cGAS-STING pathway ameliorates cellular hallmarks of aging, reduces tissue degeneration, and extends the lifespan of progeria mice. Our study reveals that a new feature of aging is the progressively reduced ability to activate the canonical cGAS-STING pathway in response to cytosolic DNA, triggering instead a non-canonical pathway that drives senescence/aging phenotypes.

Significance Statement

Our study provides novel insights into the mechanisms driving sterile inflammation in aging and progeria. We reveal a previously unrecognized characteristic of aging cells: the progressive loss of ability to activate the canonical response to foreign or self-DNA at the cytoplasm. Instead, aging, senescent, and progeria cells activate inflammatory programs via a non-conventional pathway driven by cGAS and the adaptor protein STING. Importantly, pharmacological inhibition of the non-canonical cGAS-STING pathway ameliorates cellular, tissue and organismal decline in a devastating accelerated aging disease (Hutchinson Gilford Progeria Syndrome), highlighting it as a promising therapeutic target for age-related pathologies.

STING activation and overcoming the challenges associated with STING agonists using ADC (antibody-drug conjugate) and other delivery systems

In current immunotherapy cGAS (cyclic GMP-AMP synthase)-STING (stimulator of interferon genes) pathway considered as most focused area after CAR-T cell. Exploitation of host immunity against cancer using STING agonists generates the most interest as a therapeutic target. Classically cGAS activation through cytoplasmic DNA generates 2'3'cGAMP that is naturally identified STING agonist. Activation of STING leads to activation of type-1 interferon response and pro-inflammatory cytokines through TBK/IRF-3, TBK/NF-κB pathways. Pro-inflammatory cytokines attract immune cells to the tumor microenvironment and type-1 interferon exposes tumor antigens to T cells and NK cells, which leads to the activation of cellular immunity against tumor cells and eliminates tumor cells. Initially bacterial-derived c-di-AMP and c-di-GMP were identified as CDNs (Cyclic-dinucleotide) STING agonists. Moreover, chemically modified CDNs and completely synthetic STING agonists have been developed. Even though the breakthrough preclinical development none of the STING agonists were approved the by FDA for cancer therapy. All identified natural CDNs have poor pharmacokinetic properties due to high hydrophilicity and negative charge. Moreover, phosphodiester bonds in CDNs are most vulnerable to enzymatic degradation. Synthetic STING agonists have an off-target effect that generates autoimmunity and cytokine storm. STING agonist needs to improve for pharmacokinetics, efficacy, and safety. In this scenario delivery systems can overcome the challenges associated with STING agonists. Here, we highlight the ways of STING agonisms as direct and indirect, and further, we also discuss the existing STING agonists associated challenges and ongoing efforts for delivery of STING agonists in the tumor microenvironment (TME) via different non-targeted carriers like Nanoparticle, Hydrogel, Micelle, Liposome. We also discussed the most advanced targeted deliveries of ADC (Antibody-drug conjugate) and aptamers-based delivery.

Unleashing the Potential of Metal Ions in cGAS-STING Activation: Advancing Nanomaterial-Based Tumor Immunotherapy

Immunotherapy is a critical modality in cancer treatment with diverse activation pathways. In recent years, the stimulator of interferon genes (STING) signaling pathway has exhibited significant potential in tumor immunotherapy. This pathway exerts notable antitumor effects by activating innate and adaptive immunity and regulating the tumor immune microenvironment. Various metal ions have been identified as effective activators of the STING pathway and, through the design and synthesis of nanodelivery platforms, have been applied in immunotherapy as well as in combination therapies, such as chemotherapy, chemodynamic therapy, photodynamic therapy, and cancer vaccines. Metal nanomaterials showcase unique advantages in immunotherapy; however, there are still aspects that require optimization. This review systematically examines existing metal-based nanomaterials, elaborates on the mechanisms by which different metal ions activate the STING pathway, and discusses their application models in tumor combination therapies. We also provide a comparative analysis of the advantages of metal nanomaterials over other treatment methods. Our exploration highlights the broad application prospects of metal nanomaterials in cancer treatment, offering new insights and directions for the advancement of tumor immunotherapy.

Crucial Roles of RSAD2/viperin in Immunomodulation, Mitochondrial Metabolism and Autoimmune Diseases

Autoimmune diseases are typically characterized by aberrant activation of immune system that leads to excessive inflammatory reactions and tissue damage. Nevertheless, precise targeted and efficient therapies are limited. Thus, studies into novel therapeutic targets for the management of autoimmune diseases are urgently needed. Radical S-adenosyl methionine domain-containing 2 (RSAD2) is an interferon-stimulated gene (ISG) renowned for the antiviral properties of the protein it encodes, named viperin. An increasing number of studies have underscored the new roles of RSAD2/viperin in immunomodulation and mitochondrial metabolism. Previous studies have shown that there is a complex interplay between RSAD2/vipeirn and mitochondria and that binding of the iron-sulfur (Fe-S) cluster is necessary for the involvement of viperin in mitochondrial metabolism. Viperin influences the proliferation and development of immune cells as well as inflammation via different signaling pathways. However, the function of RSAD2/viperin varies in different studies and a comprehensive overview of this emerging theme is lacking. This review will describe the characteristics of RSAD2/viperin, decipher its function in immunometabolic processes, and clarify the crosstalk between RSAD2/viperin and mitochondria. Furthermore, we emphasize the crucial roles of RSAD2 in autoimmune diseases and its potential application value.

The cGAS-STING pathway in HIV-1 and Mycobacterium tuberculosis coinfection

Mycobacterium tuberculosis (M. tuberculosis) infection is the most common opportunistic infection in human immunodeficiency virus-1 (HIV-1)-infected individuals, and the mutual reinforcement of these two pathogens may accelerate disease progression and lead to rapid mortality. Therefore, HIV-1/M. tuberculosis coinfection is one of the major global public health concerns. HIV-1 infection is the greatest risk factor for M. tuberculosis infection and increases the likelihood of endogenous relapse and exogenous reinfection with M. tuberculosis. Moreover, M. tuberculosis further increases HIV-1 replication and the occurrence of chronic immune activation, accelerating the progression of HIV-1 disease. Exploring the pathogenesis of HIV-1/M. tuberculosis coinfections is essential for the development of novel treatments to reduce the global burden of tuberculosis. Innate immunity, which is the first line of host immune defense, plays a critical role in resisting HIV-1 and M. tuberculosis infections. The role of the cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) signaling pathway, which is a major DNA-sensing innate immune signaling pathway, in HIV-1 infection and M. tuberculosis infection has been intensively studied. This paper reviews the role of the cGAS-STING signaling pathway in HIV-1 infection and M. tuberculosis infection and discusses the possible role of this pathway in HIV-1/M. tuberculosis coinfection to provide new insight into the pathogenesis of HIV-1/M. tuberculosis coinfection and the development of novel therapeutic strategies.

A novel biosensor for the spatiotemporal analysis of STING activation during innate immune responses to dsDNA

The cGAS-STING signalling pathway has a central role in the innate immune response to extrinsic and intrinsic sources of cytoplasmic dsDNA. At the core of this pathway is cGAS-dependent production of the intra- and extra-cellular messenger cGAMP, which activates STING and leads to IRF3-dependent expression of cytokines and interferons. Despite its relevance to viral and bacterial infections, cell death, and genome instability, the lack of specific live-cell reporters has precluded spatiotemporal analyses of cGAS-STING signalling. Here, we generate a fluorescent biosensor termed SIRF (STING-IRF3), which reports on the functional interaction between activated STING and IRF3 at the Golgi. We show that cells harbouring SIRF react in a time- and concentration-dependent manner both to STING agonists and to microenvironmental cGAMP. We demonstrate that the new biosensor is suitable for single-cell characterisation of immune responses to HSV-1 infection, mtDNA release upon apoptosis, or other sources of cytoplasmic dsDNA. Furthermore, our results indicate that STING signalling is not activated by ruptured micronuclei, suggesting that other cytosolic pattern recognition receptors underlie the interferon responses to chromosomal instability.

Regulation of the cGAS-STING Pathway

The cGAS-cGAMP-STING pathway is essential for immune defense against pathogens. Upon binding DNA, cGAS synthesizes cGAMP, which activates STING, leading to potent innate immune effector responses. However, lacking specific features to distinguish between self and nonself DNA, cGAS-STING immunity requires precise regulation to prevent aberrant activation. Several safeguard mechanisms acting on different levels have evolved to maintain tolerance to self DNA and ensure immune homeostasis under normal conditions. Disruption of these safeguards can lead to erroneous activation by self DNA, resulting in inflammatory conditions but also favorable antitumor immunity. Insights into structural and cellular checkpoints that control and terminate cGAS-STING signaling are essential for comprehending and manipulating DNA-triggered innate immunity in health and disease.

STING Activation in Various Cell Types in Metabolic Dysfunction-Associated Steatotic Liver Disease

BACKGROUND

During the hepatic histological progression in metabolic dysfunction-associated steatotic liver disease (MASLD), the immunological mechanisms play a the pivotal role, especially when progressing to metabolic dysfunction-associated steatohepatitis (MASH). The discovery of the stimulator of interferon genes (STING) marked a significant advancement in understanding the immune system.

METHODS

We searched literature on STING involved in MASLD in PubMed to summarise the role of intrahepatic or extrahepatic STING signal pathways and the potential agonists or inhibitors of STING in MASLD.

RESULTS

Besides inflammation and type I interferon response induced by STING activation in the intrahepatic or extrahepatic immune cells, STING activation in hepatocytes leads to protein aggregates and lipid deposition. STING activation in hepatic macrophages inhibits autophagy in hepatocytes and promotes hepatic stellate cells (HSCs) activation. STING activation in HSCs promotes HSC activation and exacerbates liver sinusoidal endothelial cells (LSECs) impairment. However, it was also reported that STING activation in hepatic macrophages promotes lipophagy in hepatocytes and STING activation in HSCs leads to HSC senescence. STING activation in LSEC, inhibits angiogenesis. For extrahepatic tissue, STING signalling participates in the regulation of the intestinal permeability, intestinal microecology and insulin action in adipocytes, which were all involved in the pathogenesis of MASLD.

CONCLUSION

There're plenty of STING ligands in MASLD. How STING activation affects the intercellular conversation in MASLD deserves thorough investigation.

Progress Update on STING Agonists as Vaccine Adjuvants

Low antigen immunogenicity poses a significant challenge in vaccine development, often leading to inadequate immune responses and reduced vaccine efficacy. Therefore, the discovery of potent immune-enhancing adjuvants is crucial. STING (stimulator of interferon genes) agonists are a promising class of adjuvants which have been identified in various immune cells and are activated in response to DNA fragments, triggering a broad range of type-I interferon-dependent immune responses. Integrating STING agonists with vaccine components is an ideal strategy to bolster vaccine-induced immunity to infections and cancer cells. Several STING agonists are currently under investigation in preclinical studies and clinical trials; however, some have shown limited efficacy, while others exhibit off-target effects. To ensure safety, they are typically delivered with carriers that exhibit high biocompatibility and insolubility. In this review, we present the latest research on natural and synthetic STING agonists that have been effectively used in vaccine development, and summarize their application in adjuvant preventive and therapeutic vaccines. Additionally, we discuss the safety of STING agonists as vaccine adjuvants by reviewing potential delivery strategies. Overall, incorporating STING agonists into vaccine formulations represents a significant advancement in vaccine research with the potential to significantly enhance immune responses and improve vaccine efficacy. However, ongoing research is still required to identify the most effective and safe delivery strategies for STING agonists, as well as to evaluate their long-term safety and efficacy in clinical trials.

ArfGAP2 promotes STING proton channel activity, cytokine transit, and autoinflammation

Stimulator of interferon genes (STING) transmits signals downstream of the cytosolic DNA sensor cyclic guanosine monophosphate-AMP synthase (cGAS), leading to transcriptional upregulation of cytokines. However, components of the STING signaling pathway, such as IRF3 and IFNAR1, are not essential for autoinflammatory disease in STING gain-of-function (STING-associated vasculopathy with onset in infancy [SAVI]) mice. Recent discoveries revealed that STING also functions as a proton channel that deacidifies the Golgi apparatus. Because pH impacts Golgi enzyme activity, protein maturation, and trafficking, we hypothesized that STING proton channel activity influences multiple Golgi functions. Here, we show that STING-mediated proton efflux non-transcriptionally regulates Golgi trafficking of protein cargos. This process requires the Golgi-associated protein ArfGAP2, a cell-type-specific dual regulator of STING-mediated proton efflux and signaling. Deletion of ArfGAP2 in hematopoietic and endothelial cells markedly reduces STING-mediated cytokine and chemokine secretion, immune cell activation, and autoinflammatory pathology in SAVI mice. Thus, ArfGAP2 facilitates STING-mediated signaling and cytokine release in hematopoietic cells, significantly contributing to autoinflammatory disease pathogenesis.

Palmitoylation of GPX4 via the targetable ZDHHC8 determines ferroptosis sensitivity and antitumor immunity

Ferroptosis is closely linked with various pathophysiological processes, including aging, neurodegeneration, ischemia-reperfusion injury, viral infection and, notably, cancer progression; however, its post-translational regulatory mechanisms remain incompletely understood. Here we revealed a crucial role of S-palmitoylation in regulating ferroptosis through glutathione peroxidase 4 (GPX4), a pivotal enzyme that mitigates lipid peroxidation. We identified that zinc finger DHHC-domain containing protein 8 (zDHHC8), an S-acyltransferase that is highly expressed in multiple tumors, palmitoylates GPX4 at Cys75. Through small-molecule drug screening, we identified PF-670462, a zDHHC8-specific inhibitor that promotes the degradation of zDHHC8, consequently attenuating GPX4 palmitoylation and enhancing ferroptosis sensitivity. PF-670462 inhibition of zDHHC8 facilitates the CD8+ cytotoxic T cell-induced ferroptosis of tumor cells, thereby improving the efficacy of cancer immunotherapy in a B16-F10 xenograft model. Our findings reveal the prominent role of the zDHHC8-GPX4 axis in regulating ferroptosis and highlight the potential application of zDHHC8 inhibitors in anticancer therapy.

Orally Bioavailable and Site-Selective Covalent STING Inhibitor Derived from a Macrocyclic Marine Diterpenoid

Pharmacological inhibition of the cGAS-STING-controlled innate immune pathway is an emerging therapeutic strategy for a myriad of inflammatory diseases. Here, we report GHN105 as an orally bioavailable covalent STING inhibitor. Late-stage diversification of the briarane-type diterpenoid excavatolide B allowed the installation of solubility-enhancing functional groups while enhancing its activity as a covalent STING inhibitor against multiple human STING variants, including the S154 variant responsible for a genetic autoimmune disease. Selectively engaging the membrane-proximal Cys91 residue of STING, GHN105 dose-dependently inhibited cGAS-STING signaling and type I interferon responses in cells and in vivo. Moreover, orally administered GHN105 exhibited on-target engagement in vivo and markedly reversed key pathological features in a delayed treatment of the acute colitis mouse model. Our study provided proof of concept that the synthetic briarane analog GHN105 serves as a safe, site-selective, and orally active covalent STING inhibitor and devises a regimen that allows long-term systemic administration.

Regulation and Function of the cGAS-STING Pathway: Mechanisms, Post-Translational Modifications, and Therapeutic Potential in Immunotherapy

Autoimmune diseases arise when the immune system attacks healthy tissues, losing tolerance for self-tissues. Normally, the immune system recognizes and defends against pathogens like bacteria and viruses. The cGAS-STING pathway, activated by pattern-recognition receptors (PRRs), plays a key role in autoimmune responses. The cGAS protein senses pathogenic DNA and synthesizes cGAMP, which induces conformational changes in STING, activating kinases IKK and TBK1 and leading to the expression of interferon genes or inflammatory mediators. This pathway is crucial in immunotherapy, activating innate immunity, enhancing antigen presentation, modulating the tumor microenvironment, and integrating into therapeutic strategies. Modulation strategies include small molecule inhibitors, oligonucleotide therapies, protein and antibody therapies, genetic and epigenetic regulation, cytokine and metabolite modulation, and nanoscale delivery systems. Post-translational modifications (PTMs) of the cGAS-STING pathway, such as phosphorylation, acetylation, ubiquitination, methylation, palmitoylation, and glycosylation, fine-tune immune responses by regulating protein activity, stability, localization, and interactions. These modifications are interconnected and collectively influence pathway functionality. We summarize the functions of cGAS-STING and its PTMs in immune and non-immune cells across various diseases, and explore potential clinical applications.

COPB1-knockdown induced type I interferon signaling activation inhibits Chlamydia psittaci intracellular proliferation

Objective

Chlamydia psittaci is a zoonotic pathogen that causes an acute disease known as psittacosis. To establish infection in host cells, Chlamydia manipulates the host cell's membrane trafficking pathways.

Methods

In this study, using fluorescently labeled C. psittaci and screening a human membrane trafficking small interfering RNA (siRNA) library, we identified 34 host proteins that influenced C. psittaci infection in HeLa cells.

Results

Among these, knockdown (KD) of two genes encoding subunits of the coatomer complex I (COPI) inhibited the pathogen's intracellular survival. Specifically, the knockdown of COPB1, a COPI subunit, significantly reduced the intracellular proliferation of C. psittaci. Mechanistically, we found that type I interferon negatively affected C. psittaci infection. Moreover, COPB1 KD disrupted the homeostasis of STING, preventing its retrieval from the Golgi back to the endoplasmic reticulum (ER), which in turn activated type I interferon signaling.

Conclusion

Together, our findings advance the understanding of the mechanisms underlying Chlamydia infection and offer potential avenues for the development of new anti-C. psittaci strategies.

The neuroimmune nexus: unraveling the role of the mtDNA-cGAS-STING signal pathway in Alzheimer's disease

The relationship between Alzheimer's disease (AD) and neuroimmunity has gradually begun to be unveiled. Emerging evidence indicates that cyclic GMP-AMP synthase (cGAS) acts as a cytosolic DNA sensor, recognizing cytosolic damage-associated molecular patterns (DAMPs), and inducing the innate immune response by activating stimulator of interferon genes (STING). Dysregulation of this pathway culminates in AD-related neuroinflammation and neurodegeneration. A substantial body of evidence indicates that mitochondria are involved in the critical pathogenic mechanisms of AD, whose damage leads to the release of mitochondrial DNA (mtDNA) into the extramitochondrial space. This leaked mtDNA serves as a DAMP, activating various pattern recognition receptors and immune defense networks in the brain, including the cGAS-STING pathway, ultimately leading to an imbalance in immune homeostasis. Therefore, modulation of the mtDNA-cGAS-STING pathway to restore neuroimmune homeostasis may offer promising prospects for improving AD treatment outcomes. In this review, we focus on the mechanisms of mtDNA release during stress and the activation of the cGAS-STING pathway. Additionally, we delve into the research progress on this pathway in AD, and further discuss the primary directions and potential hurdles in developing targeted therapeutic drugs, to gain a deeper understanding of the pathogenesis of AD and provide new approaches for its therapy.

STING in cancer immunoediting: Modeling tumor-immune dynamics throughout cancer development

Cancer immunoediting is a dynamic process of tumor-immune system interaction that plays a critical role in cancer development and progression. Recent studies have highlighted the importance of innate signaling pathways possessed by both cancer cells and immune cells in this process. The STING molecule, a pivotal innate immune signaling molecule, mediates DNA-triggered immune responses in both cancer cells and immune cells, modulating the anti-tumor immune response and shaping the efficacy of immunotherapy. Emerging evidence has shown that the activation of STING signaling has dual opposing effects in cancer progression, simultaneously provoking and restricting anti-tumor immunity, and participating in every phase of cancer immunoediting, including immune elimination, equilibrium, and escape. In this review, we elucidate the roles of STING in the process of cancer immunoediting and discuss the dichotomous effects of STING agonists in the cancer immunotherapy response or resistance. A profound understanding of the sophisticated roles of STING signaling pathway in cancer immunoediting would potentially inspire the development of novel cancer therapeutic approaches and overcome the undesirable protumor effects of STING activation.

DSTYK phosphorylates STING at late endosomes to promote STING signaling

Stimulator of interferon genes (STING) is essential for innate immune pathway activation in response to pathogenic DNA. Proper activation of STING signaling requires STING translocation and phosphorylation. Here, we show that dual serine/threonine and tyrosine protein kinase (DSTYK) directly phosphorylates STING Ser366 at late endosomes to promote the activation of STING signaling. We find that TBK1 promotes STING post-Golgi trafficking via its kinase activity, thereby enabling the interaction between DSTYK and STING. We also demonstrate that DSTYK and TBK1 can both promote STING phosphorylation at late endosomes. Using an in vivo Dstyk-knockout model, we showed that mice deficient in DSTYK demonstrate reduced STING signaling activation and are more susceptible to infection with a DNA virus. Together, we reveal the previously unknown cellular function of DSTYK in phosphorylating STING and our findings provide insights into the mechanism of STING signaling activation at late endosomes.

Spatial proteomics identifies a CRTC-dependent viral signaling pathway that stimulates production of interleukin-11

Appropriate cellular recognition of viruses is essential for the generation of an effective innate and adaptive immune response. Viral sensors and their downstream signaling components thus provide a crucial first line of host defense. Many of them exhibit subcellular relocalization upon activation, resulting in the expression of interferon and antiviral genes. To comprehensively identify signaling factors, we analyzed protein relocalization on a global scale during viral infection. cAMP-responsive element-binding protein (CREB)-regulated transcription coactivators 2 and 3 (CRTC2/3) exhibited early cytoplasmic-to-nuclear translocation upon infection with multiple viruses in diverse cell types. This movement was dependent on mitochondrial antiviral signaling protein (MAVS), cyclo-oxygenase proteins, and protein kinase A. A key effect of CRTC2/3 translocation is transcription of the fibro-inflammatory cytokine interleukin (IL)-11. This may be important clinically in viral infections associated with fibrosis, including SARS-CoV-2. Nuclear translocation of CRTC2/3 is, therefore, identified as an important pathway in the context of viral infection.

Regulation of pattern recognition receptor signaling by palmitoylation

Pattern recognition receptors (PRRs), consisting of Toll-like receptors, RIG-I-like receptors, cytosolic DNA sensors, and NOD-like receptors, sense exogenous pathogenic molecules and endogenous damage signals to maintain physiological homeostasis. Upon activation, PRRs stimulate the sensitization of nuclear factor κB, mitogen-activated protein kinase, TANK-binding kinase 1-interferon (IFN) regulatory factor, and inflammasome signaling pathways to produce inflammatory factors and IFNs to activate Janus kinase/signal transducer and activator of transcription signaling pathways, resulting in anti-infection, antitumor, and other specific immune responses. Palmitoylation is a crucial type of post-translational modification that reversibly alters the localization, stability, and biological activity of target molecules. Here, we discuss the available knowledge on the biological roles and underlying mechanisms linked to protein palmitoylation in modulating PRRs and their downstream signaling pathways under physiological and pathological conditions. Moreover, recent advances in the use of palmitoylation as an attractive therapeutic target for disorders caused by the dysregulation of PRRs were summarized.

Bidirectional regulation of the cyclic guanosine monophosphate-adenosine monophosphate synthase-stimulator of interferon gene pathway and its impact on hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) ranks as the fourth leading cause of cancer-related deaths in China, and the treatment options are limited. The cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) activates the stimulator of interferon gene (STING) signaling pathway as a crucial immune response pathway in the cytoplasm, which detects cytoplasmic DNA to regulate innate and adaptive immune responses. As a potential therapeutic target, cGAS-STING pathway markedly inhibits tumor cell proliferation and metastasis, with its activation being particularly relevant in HCC. However, prolonged pathway activation may lead to an immunosuppressive tumor microenvironment, which fostering the invasion or metastasis of liver tumor cells.

AIM

To investigate the dual-regulation mechanism of cGAS-STING in HCC.

METHODS

This review was conducted according to the PRISMA guidelines. The study conducted a comprehensive search for articles related to HCC on PubMed and Web of Science databases. Through rigorous screening and meticulous analysis of the retrieved literature, the research aimed to summarize and elucidate the impact of the cGAS-STING pathway on HCC tumors.

RESULTS

All authors collaboratively selected studies for inclusion, extracted data, and the initial search of online databases yielded 1445 studies. After removing duplicates, the remaining 964 records were screened. Ultimately, 55 articles met the inclusion criteria and were included in this review.

CONCLUSION

Acute inflammation can have a few inhibitory effects on cancer, while chronic inflammation generally promotes its progression. Extended cGAS-STING pathway activation will result in a suppressive tumor microenvironment.

Mitochondrial DAMPs: Key mediators in neuroinflammation and neurodegenerative disease pathogenesis

Neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS) are increasingly linked to mitochondrial dysfunction and neuroinflammation. Central to this link are mitochondrial damage-associated molecular patterns (mtDAMPs), including mitochondrial DNA, ATP, and reactive oxygen species, released during mitochondrial stress or damage. These mtDAMPs activate inflammatory pathways, such as the NLRP3 inflammasome and cGAS-STING, contributing to the progression of neurodegenerative diseases. This review delves into the mechanisms by which mtDAMPs drive neuroinflammation and discusses potential therapeutic strategies targeting these pathways to mitigate neurodegeneration. Additionally, it explores the cross-talk between mitochondria and the immune system, highlighting the complex interplay that exacerbates neuronal damage. Understanding the role of mtDAMPs could pave the way for novel treatments aimed at modulating neuroinflammation and slowing disease progression, ultimately improving patient outcome.

zDHHC-Mediated S-Palmitoylation in Skin Health and Its Targeting as a Treatment Perspective

S-acylation, which includes S-palmitoylation, is the only known reversible lipid-based post-translational protein modification. S-palmitoylation is mediated by palmitoyl acyltransferases (PATs), a family of 23 enzymes commonly referred to as zDHHCs, which catalyze the addition of palmitate to cysteine residues on specific target proteins. Aberrant S-palmitoylation events have been linked to the pathogenesis of multiple human diseases. While there have been advances in elucidating the molecular mechanisms underlying the pathogenesis of various skin conditions, there remain gaps in the knowledge, specifically with respect to the contribution of S-palmitoylation to the maintenance of skin barrier function. Towards this goal, we performed PubMed literature searches relevant to S-palmitoylation in skin to define current knowledge and areas that may benefit from further research studies. Furthermore, to identify alterations in gene products that are S-palmitoylated, we utilized bioinformatic tools such as SwissPalm and analyzed relevant data from publicly available databases such as cBioportal. Since the targeting of S-palmitoylated targets may offer an innovative treatment perspective, we surveyed small molecules inhibiting zDHHCs, including 2-bromopalmitate (2-BP) which is associated with off-target effects, and other targeting strategies. Collectively, our work aims to advance both basic and clinical research on skin barrier function with a focus on zDHHCs and relevant protein targets that may contribute to the pathogenesis of skin conditions such as atopic dermatitis, psoriasis, and skin cancers including melanoma.

Discovery of an Orally Bioavailable STING Inhibitor with In Vivo Anti-Inflammatory Activity in Mice with STING-Mediated Inflammation

The cyclic GMP-AMP synthase (cGAS)-stimulator of the interferon genes (STING) pathway plays a key role in triggering interferon and inflammatory responses against microbial invasion or tumor. However, aberrant activation of the cGAS-STING pathway is associated with a variety of inflammatory and autoimmune diseases, and thus inhibition of STING is regarded as a potential new approach to treating these diseases. Herein, we report a series of novel indolyl-urea derivatives as STING inhibitors. The representative compound 42 exhibited potent STING inhibitory activity, acceptable pharmacokinetic properties, and good in vivo safety profiles. Mechanistically, 42 could block the palmitoylation of the STING protein and STING downstream signaling. Importantly, oral administration of 42 could effectively suppress STING-mediated inflammation in 10-carboxymethyl-9-acridanone (CMA)-treated mouse and Trex1-/- mouse. Together, compound 42 represents a promising STING inhibitor for treating STING-associated inflammatory and autoimmune diseases.

The cross-talk between the cGAS-STING signaling pathway and chronic inflammation in the development of musculoskeletal disorders

Musculoskeletal disorders (MSDs) comprise diverse conditions affecting bones, joints, and muscles, leading to pain and loss of function, and are one of the most prevalent and major global health concerns. One of the hallmarks of MSDs is DNA damage. Once accumulated in the cytoplasm, the damaged DNA is sensed by the cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) pathway, which triggers the induction of type I interferons and inflammatory cytokines. Thus, this pathway connects the musculoskeletal and immune systems. Inhibitors of cGAS or STING have shown promising therapeutic effects in the pre-clinical models of several MSDs. Systemic, chronic, low-grade inflammation (SCLGI) underlies the development and maintenance of many MSDs. Failure to resolve SCLGI has been hypothesized to play a critical role in the development of chronic diseases, suggesting that the successful resolution of SCLGI will result in the alleviation of their related symptomatology. The process of inflammation resolution is feasible by specialized pro-resolving mediators (SPMs), which are enzymatically generated from dietary essential polyunsaturated fatty acids (PUFAs). The supplementation of SPMs or their stable, small-molecule mimetics and receptor agonists has revealed beneficial effects in inflammation-related animal models, including arthropathies, osteoporosis, and muscle dystrophy, suggesting a translational potential in MSDs. In this review, we substantiate the hypothesis that the use of cGAS-STING signaling pathway inhibitors together with SCLG-resolving compounds may serve as a promising new therapeutic approach for MSDs.

The STING signaling pathways and bacterial infection

As antibiotic-resistant bacteria continue to emerge frequently, bacterial infections have become a significant and pressing challenge to global public health. Innate immunity triggers the activation of host responses by sensing "non-self" components through various pattern recognition receptors (PRRs), serving as the first line of antibacterial defense. Stimulator of interferon genes (STING) is a PRR that binds with cyclic dinucleotides (CDN) to exert effects against bacteria, viruses, and cancer by inducing the production of type I interferon and inflammatory cytokines, and facilitating regulated cell death. Currently, drugs targeting the STING signaling pathway are predominantly applied in the fields of modulating host immune defense against cancer and viral infections, with relatively limited application in treating bacterial infections. Given the significant immunomodulatory functions of STING in the interaction between bacteria and hosts, this review summarizes the research progress on STING signaling pathways and their roles in bacterial infection, as well as the novel functions of STING modulators, aiming to offer insights for the development of antibacterial drugs.

A compendium of Amplification-Related Gain Of Sensitivity genes in human cancer

While the effect of amplification-induced oncogene expression in cancer is known, the impact of copy-number gains on "bystander" genes is less understood. We create a comprehensive map of dosage compensation in cancer by integrating expression and copy number profiles from over 8000 tumors in The Cancer Genome Atlas and cell lines from the Cancer Cell Line Encyclopedia. Additionally, we analyze 17 cancer open reading frame screens to identify genes toxic to cancer cells when overexpressed. Combining these approaches, we propose a class of 'Amplification-Related Gain Of Sensitivity' (ARGOS) genes located in commonly amplified regions, yet expressed at lower levels than expected by their copy number, and toxic when overexpressed. We validate RBM14 as an ARGOS gene in lung and breast cancer cells, and suggest a toxicity mechanism involving altered DNA damage response and STING signaling. We additionally observe increased patient survival in a radiation-treated cancer cohort with RBM14 amplification.

HIV-1 Vpu and SARS-CoV-2 ORF3a proteins disrupt STING-mediated activation of antiviral NF-κB signaling

Activation of the stimulator of interferon genes (STING) pathway by cytosolic DNA leads to the activation of the transcription factors interferon regulatory factor 3 (IRF3) and nuclear factor κB (NF-κB). Although many viruses produce proteins that inhibit IRF3-dependent antiviral responses, some viruses produce proteins that inhibit STING-induced NF-κB activation without blocking IRF3 activation. Here, we found that STING-activated, NF-κB-dependent, and IRF3-independent innate immunity inhibited the replication of the DNA virus herpes simplex virus type 1 (HSV-1), the RNA virus coxsackievirus A16 (CV-A16), and the retrovirus HIV-1. The HIV-1 nonstructural protein Vpu bound to STING and prevented it from interacting with the upstream NF-κB pathway kinase inhibitor of NF-κB subunit β (IKKβ), thus blocking NF-κB signaling. This function of Vpu was conserved among Vpu proteins from diverse HIV-1 and simian immunodeficiency virus strains and was distinct from its action in disrupting other host antiviral pathways. Furthermore, the ORF3a protein from the coronavirus SARS-CoV-2 also promoted viral replication by interacting with STING and blocking STING-induced activity of NF-κB but not of IRF3. These findings demonstrate that diverse viral proteins have convergently evolved to selectively inhibit NF-κB-mediated innate immunity downstream of STING activation, suggesting that targeting this pathway may represent a promising antiviral strategy.

Endothelial STING-JAK1 interaction promotes tumor vasculature normalization and antitumor immunity

Stimulator of interferon genes (STING) agonists have been developed and tested in clinical trials for their antitumor activity. However, the specific cell population(s) responsible for such STING activation-induced antitumor immunity have not been completely understood. In this study, we demonstrated that endothelial STING expression was critical for STING agonist-induced antitumor activity. STING activation in endothelium promoted vessel normalization and CD8+ T cell infiltration - which required type I IFN (IFN-I) signaling- but not IFN-γ or CD4+ T cells. Rather than an upstream adaptor for inducing IFN-I signaling, STING acted downstream of interferon-α/β receptor (IFNAR) in endothelium for the JAK1-STAT signaling activation. Mechanistically, IFN-I stimulation induced JAK1-STING interaction and promoted JAK1 phosphorylation, which involved STING palmitoylation at the Cysteine 91 site but not its C-terminal tail (CTT) domain. Endothelial STING and JAK1 expression was significantly associated with immune cell infiltration in patients with cancer, and STING palmitoylation level correlated positively with CD8+ T cell infiltration around STING-positive blood vessels in tumor tissues from patients with melanoma. In summary, our findings uncover a previously unrecognized function of STING in regulating JAK1/STAT activation downstream of IFN-I stimulation and provide a new insight for future design and clinical application of STING agonists for cancer therapy.

Protein palmitoylation is involved in regulating mouse sperm motility via the signals of calcium, protein tyrosine phosphorylation and reactive oxygen species

BACKGROUND

Protein palmitoylation, a critical posttranslational modification, plays an indispensable role in various cellular processes, including the regulation of protein stability, mediation of membrane fusion, facilitation of intracellular protein trafficking, and participation in cellular signaling pathways. It is also implicated in the pathogenesis of diseases, such as cancer, neurological disorders, inflammation, metabolic disorders, infections, and neurodegenerative diseases. However, its regulatory effects on sperm physiology, particularly motility, remain unclear. This study aimed to elucidate the mechanism by which protein palmitoylation governs sperm motility.

METHODS

Protein palmitoylation in situ in mouse sperm was observed using innovative click chemistry. Sperm motility and motion parameters were evaluated using a computer-assisted sperm analyzer (CASA) after treatment with 2-bromopalmitic acid (2BP), a specific inhibitor of protein palmitoylation. Protein palmitoylation levels were confirmed by the acyl-biotin exchange (ABE) method. The interplay between protein palmitoylation, protein tyrosine phosphorylation, and intracellular calcium was investigated using Western blotting, ABE method, and fluorescent probes. The regulation of reactive oxygen species was also examined using fluorescent probes.

RESULTS

Localized patterns and dynamics of protein palmitoylation in distinct sperm regions were revealed, including the midpiece, post-acrosomal region, acrosome, and head. Alterations in protein palmitoylation in sperm were observed under in vitro physiological conditions. Treatment with 2BP significantly affected sperm motility and motion parameters. The study revealed interactions between protein palmitoylation, including heat shock protein 90, and protein kinase A/protein kinase C-associated protein tyrosine phosphorylation and intracellular calcium. Additionally, protein palmitoylation was found to be involved in reactive oxygen species regulation.

CONCLUSIONS

Protein palmitoylation regulates sperm motility through calcium signaling, protein tyrosine phosphorylation, and reactive oxygen species. This study revealed the characteristics of protein palmitoylation in sperm and its role in regulating sperm motility, thereby providing novel insights into the causes of asthenozoospermia associated with sperm motility in humans.

Regulation of cGAS-STING signalling and its diversity of cellular outcomes

The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signalling pathway, which recognizes both pathogen DNA and host-derived DNA, has emerged as a crucial component of the innate immune system, having important roles in antimicrobial defence, inflammatory disease, ageing, autoimmunity and cancer. Recent work suggests that the regulation of cGAS-STING signalling is complex and sophisticated. In this Review, we describe recent insights from structural studies that have helped to elucidate the molecular mechanisms of the cGAS-STING signalling cascade and we discuss how the cGAS-STING pathway is regulated by both activating and inhibitory factors. Furthermore, we summarize the newly emerging understanding of crosstalk between cGAS-STING signalling and other signalling pathways and provide examples to highlight the wide variety of cellular processes in which cGAS-STING signalling is involved, including autophagy, metabolism, ageing, inflammation and tumorigenesis.

Adaptor-Mediated Trafficking of Tank Binding Kinase 1 During Diverse Cellular Processes

The serine/threonine kinase, Tank Binding Kinase 1 (TBK1), drives distinct cellular processes like innate immune signaling, selective autophagy, and mitosis. It is suggested that the translocation and activation of TBK1 at different subcellular locations within the cell, downstream of diverse stimuli, are driven by TBK1 adaptor proteins forming a complex directly or indirectly with TBK1. Various TBK1 adaptors and associated proteins like NAP1, TANK, SINTBAD, p62, optineurin (OPTN), TAX1BP1, STING, and NDP52 have been identified in facilitating TBK1 activation and recruitment with varying overlapping redundancy. This review focuses on what is known about these proteins, their interactions with TBK1, and the functional consequences of these associations. We shed light on underexplored areas of research on these TBK1 binding partners while emphasizing how future research is required to understand the function and flexibility of TBK1 signaling and crosstalk or regulation between different biological processes.

Investigation of protein post-translational modifications with site-specifically incorporated non-canonical amino acids

Despite the important functions of protein post-translational modifications (PTMs) in numerous cellular processes, understanding the biological roles of PTMs remains quite challenging. Here, we summarize our efforts in recent years to incorporate a variety of non-canonical amino acids (ncAAs) to study the biological functions of protein PTMs in mammalian cells, with a focus on the use of ncAA tools to probe the biological functions of various protein PTMs. We design length-tunable lipidation mimics for studying lipidation function and designing protein drugs. We highlight the use of genetically encoded lysine aminoacylations as chemical baits to identify aminoacylated lysine ubiquitination. Finally, we discuss the use of genetically encoded electron-rich Trp derivatives to design binding affinity-enhancing histone methylations readers.

Nanomedicines harnessing cGAS-STING pathway: sparking immune revitalization to transform 'cold' tumors into 'hot' tumors

cGAS-STING pathway stands at the forefront of innate immunity and plays a critical role in regulating adaptive immune responses, making it as a key orchestrator of anti-tumor immunity. Despite the great potential, clinical outcomes with cGAS-STING activators have been disappointing due to their unfavorable in vivo fate, signaling an urgent need for innovative solutions to bridge the gap in clinical translation. Recent advancements in nanotechnology have propelled cGAS-STING-targeting nanomedicines to the cutting-edge of cancer therapy, leveraging precise drug delivery systems and multifunctional platforms to achieve remarkable region-specific biodistribution and potent therapeutic efficacy. In this review, we provide an in-depth exploration of the molecular mechanisms that govern cGAS-STING signaling and its potential to dynamically modulate the anti-tumor immune cycle. We subsequently introduced several investigational cGAS-STING-dependent anti-tumor agents and summarized their clinical trial progress. Additionally, we provided a comprehensive review of the unique advantages of cGAS-STING-targeted nanomedicines, highlighting the transformative potential of nanotechnology in this field. Furthermore, we comprehensively reviewed and comparatively analyzed the latest breakthroughs cGAS-STING-targeting nanomedicine, focusing on strategies that induce cytosolic DNA generation via exogenous DNA delivery, chemotherapy, radiotherapy, or dynamic therapies, as well as the nanodelivery of STING agonists. Lastly, we discuss the future prospects and challenges in cGAS-STING-targeting nanomedicine development, offering new insights to bridge the gap between mechanistic research and drug development, thereby opening new pathways in cancer treatment.

Classification and functional characterization of regulators of intracellular STING trafficking identified by genome-wide optical pooled screening

Stimulator of interferon genes (STING) traffics across intracellular compartments to trigger innate responses. Mutations in factors regulating this process lead to inflammatory disorders. To systematically identify factors involved in STING trafficking, we performed a genome-wide optical pooled screen (OPS). Based on the subcellular localization of STING in 45 million cells, we defined 464 clusters of gene perturbations based on their cellular phenotypes. A secondary, higher-dimensional OPS identified 73 finer clusters. We show that the loss of the gene of unknown function C19orf25, which clustered with USE1, a protein involved in Golgi-to-endoplasmic reticulum (ER) transport, enhances STING signaling. Additionally, HOPS deficiency delayed STING degradation and consequently increased signaling. Similarly, GARP/RIC1-RGP1 loss increased STING signaling by delaying STING Golgi exit. Our findings demonstrate that genome-wide genotype-phenotype maps based on high-content cell imaging outperform other screening approaches and provide a community resource for mining factors that impact STING trafficking and other cellular processes.

COPA Syndrome-From Pathogenesis to Treatment

Coatomer subunit α (COPA) syndrome is a mendelian autosomal dominant immune dysregulation disease characterized by early onset lung disease in the form of diffuse alveolar hemorrhaging or interstitial lung disease, frequently associated with arthritis, glomerulonephritis, and high titer autoantibodies usually mimicking other autoimmune diseases. While immunosuppressive medication has been effective in controlling arthritis, data on long-term lung disease control remains scarce, which poses a real challenge as the progression of lung disease is the main cause of poor life expectancy in COPA patients. Nevertheless, JAK inhibitor therapy seems to be the most promising therapeutic choice now.

SOX2-induced IL1α-mediated immune suppression drives epithelial dysplasia malignant transformation

Squamous cell carcinomas (SCC) are often preceded by potentially malignant precursor lesions, most of which remain benign. The terminal exhaustion phenotypes of effector T-cells and the accumulation of myeloid-derived suppressor cells (MDSC) have been thoroughly characterized in established SCC. However, it is unclear what precancerous lesions harbor a bona fide high risk for malignant transformation and how precancerous epithelial dysplasia drives the immune system to the point of no return. Here we show that expression of SRY-box transcription factor 2 (SOX2) in precancerous lesions imparts an irreversible risk that recruits suppressive myeloid cells by promoting the release of CCL2. We developed a unique genetically engineered mouse model (GEMM) to recapitulate the malignant transformation of epithelial dysplasia to SCC in the oral mucosa with high histologic and phenotypic fidelity. Using a combination of longitudinal human specimens and the Sox2-GEMM, we found that the myeloid cells in precancerous epithelial dysplasia exhibit a distinctive dichotomous profile featuring high levels of IL-1α-SLC2A1 and low levels of type-I interferon (IFN-I) signatures, which occurs before SCC emerges histologically. Brief priming of myeloid cells with IL-1α desensitizes them to IFN-I agonists and makes myeloid-derived suppressor cells (MDSC) even more suppressive of T-cell activation. Mechanistically, IL-1 activation represses the expression of DHHC3/7 enzymes, which are responsible for the palmitoylation of stimulator of interferon genes (STING). Early blockade of IL1 signaling using pharmacologic and genetic approaches similarly reduces MDSC and SLC2A1high myeloid cells, suppresses epithelial dysplasia transformation, and extends survival. This work establishes a previously unrecognized SOX2-CCL2-IL1 pathway that leads to irreversible immune escape when precancerous epithelial lesions transform.